unpack failed --- is my repos broken?

Dear All

I have several git repositories on a server, with which I'm communicating using smart-http. Push and pull is all going fine. Until this morning, one of the repositories is not allowing pushes:

     $ git push
     Password: ...
     Counting objects: 5, done.
     Delta compression using up to 2 threads.
     Compressing objects: 100% (3/3), done.
     Writing objects: 100% (3/3), 410 bytes, done.
     Total 3 (delta 2), reused 0 (delta 0)
     error: unpack failed: unpack-objects abnormal exit

Other repositories on the same server (and under the same /var/www/git/ directory) are working fine.

I have googled around and this doesn't seem to be an uncommon problem, but I haven't found a solution.

Does the above mean this repository is broken and I should rescue or replace it (as in "How to fix a broken repository?" on the git wiki [1])?

Is smart-http not entirely reliable? In which case what is the preferred way to communicate remotely (we need to push as well as pull; there are a very small number of active developers)?

With thanks and best wishes

Ivan

[1] How to fix a broken repository?
     
http://git.wiki.kernel.org/index.php/GitFaq#How_to_fix_a_broken_repository.3F